At present, digital broadcasting is rapidly supplanting analog broadcasting. Thus, the amount of digital broadcast content has been rapidly increased. As digital broadcast content, content used to display a three-dimensional (3D) image signal as a 3D image have been created, in addition to content used to display a two-dimensional (2D) image signal as a 2D image.
3D image display technology functions based on the principle of binocular disparity: the difference in image location of an object as seen by the left and right eyes of a viewer, and is divided into a glasses method (shutter glasses method), a non-glasses method, and a full-3D method. The glasses method refers to a method for enabling a viewer to wear glasses having a special function in order to view a stereoscopic image. The glasses method is largely divided into a shutter glasses method for alternately opening and closing left and right shutters and a polarization method for mounting different circularly polarizing plates in left-eye and right-eye glass lenses.